I do not use IDLE (except for testing) and would not be affected by such a change.

However, many tutorials and books intended for beginners instruct users to use IDLE, with the assumption that it is available out of the box. Removing IDLE would immediately make instructions from those tutorials and books obsolete and needlessly confuse beginners who often struggle installing anything additional to a basic Python installation.

I just checked and if I right-click on a Python file, I see 29 entries in the contextual menu, 28 of which would be unaffected if IDLE would be removed.

If IDLE were not included by default (or if it required clicking on a checkbox), I think that the number of questions in various beginners forum about installing IDLE would quickly become a real annoyance for people that strive to help beginners.